The Sure Thing

Don't believe the deniers—science is a resolute enemy of erroneous conventional wisdom.

One of the great joys of running a magazine is getting to hear readers react to our stories. Whenever DISCOVER publishes an article about global warming, the responses are particularly passionate. Many letters take issue with individual points of climate science, but I am particularly intrigued by the ones that aim wider, targeting the very concept of scientific certainty.

This critique is often expressed as some variant on “right, and scientists also used to think the world was flat.” If they could all be wrong about such a fundamental fact, the thinking goes, how can we trust they aren’t being fooled again? The argument has a couple huge problems, though. For one, scientists never thought the world was flat. Even in ancient Greece, educated people understood that our planet is round. Earth’s shadow on the moon during a lunar eclipse is clear evidence of that.

More broadly, the flat-earth critique illustrates the opposite of what it claims. Scientists are typically in the vanguard in rejecting old ideas and embracing novel, counterintuitive ones when the evidence becomes compelling. The greatest resistance has generally come from the outside, when those new ideas ran counter to religious doctrine (Galileo versus the Catholic Church) or business practices (Ignaz Semmelweis’s battle with the 19th-century medical establishment to institute hygienic rules in hospitals, for instance). And evidence, once collected, does not go away. Galileo didn’t discredit prior astronomical observations; he added to them. Likewise, more research can deepen our understanding of climate, but it cannot overrule the evidence that the Earth is growing warmer.

Yet a number of climate-skeptic writers suggest otherwise. They state that researchers in the 1970s predominantly believed in global cooling, implying that climate data have been discredited once and (presumably) might be again. Fortunately, this claim is easy to fact check. A tour around the Internet traces most of the cooling references back to a single, hyperbolic story from Newsweek in April 1975. More telling, a detailed literature analysis by climatologist Thomas Peterson of NOAA and colleagues shows that, even in the 1970s, the bulk of the climate papers tentatively foresaw a warming trend.

Plenty of uncertainties still remain—in how climate change will play out, and in how we should respond. The lively debate about climate and water supply in this issue is evidence of that. But I am confident that the scientists at least have their feet firmly planted on the good old spherical Earth.